1 Bug Id: 4095849 2 Category: kernel 3 Subcategory: syscall 4 State: evaluated 5 Synopsis: time_constant value >6 with PLL in use leads to integer divide 6 zero trap panic 7 Description: 8If the time_constant parameter is 7 or higher, and the phase-lock looping model 9is in use, the system will take a "integer divide zero trap" panic in 10the clock routine as soon as the time_offset becomes non-zero. 11 12time_constant defaults to 0. The only place it is set is in the ntp_adjtime 13system call, from the 'constant' element of the timex structure argument. 14 15 Work around: 16Never set the constant element of the timex structure passed to ntp_adjtime to 17a value larger than 6. 18 19satish.mynam@Eng 1998-04-30 201. Use Sun's version of NTP software instead of PD version. This problem 21is not seen with Sun's NTP version (which is mostly eqivalent to PD NTP 3.4 22plus some Sun's local functionality futures). 23 242. Workaround for the public domain NTP version ONLY: 25 ===================================================== 26The workaround for public domain NTP version is to disable the 27KERNEL_PLL from the NTP code. This way ntp_Adjtime() system call is 28totally bypassed without sacrificing any of the functionality of the 29NTP. The only hit you might see is the way kernel precision timminig 30is done without the PLL algorithm in the kernel. 31 32 The easiest way to disable ntp_adjtime option is(without changing 33 any makefiles or other config files) to disable the KERNEL_PLL 34 value in the ./config.h file. 35 36After doing a ./configure for probing for all the necessary tools(compilers, 37os version, libraries), please comment out KERNEL_PLL macro in 38the ./config.h file. This will disable the KERNEL_PLL part of the source 39code and the newly obtained xntpd is just similar to the old one but it 40does not use ntp_adjtime() system call. This prevents it from panic'ng 41the kernel. 42 43/*#define KERNEL_PLL 1*/ 44 45I complied a new xntpd binary this way and it does nothave any ntp_adjtime() 46related stuff. 47 48Default: 49======= 50/net/divya/export/home/mynam/public_domain/ntp/xntp3-5.92/xntpd>strings 51xntpd | 52grep ntp_adjtime 53354:adj_frequency: ntp_adjtime failed: %m 54357:loop_config: ntp_adjtime() failed: %m 55435:get_kernel_info: ntp_adjtime() failed: %m 56 57With KERNEL_PLL disabled in config.h file 58-======================= 59 60/net/divya/export/home/mynam/public_domain/ntp/xntp3-5.92/xntpd>strings 61xntpd.nopll | grep ntp_adjtime 62 63 Integrated in releases: 64 Duplicate of: 65 Patch id: 66 See also: 4133517 67 Summary: 68If the time_constant parameter is 7 or higher, and the phase-lock looping model 69is in use, the system will take a "integer divide zero trap" panic in 70the clock routine as soon as the time_offset becomes non-zero. 71 72time_constant defaults to 0. The only place it is set is in the ntp_adjtime 73system call, from the 'constant' element of the timex structure argument. 74---------------------------------------------------------------------------- 75